Several changes in Kruskal alg.
- Input object interface was changed to an STL compatible one.
- template parameters of class KruskalPairVec has been simplified.
- (the most of) the names meet the naming conventions.
- a lot of (but still not enough) documentation has been added.
- class KruskalMapVec has been commented out.

 ./preflow_demo_leda < $1

 ./preflow_demo_boost < $1

 ./preflow_demo_jacint < $1

 ./preflow_demo_athos < $1

 ./edmonds_karp_demo < $1

 ./edmonds_karp_demo_alpar < $1

 ./edmonds_karp_demo_boost < $1